1. Technical Field of the Invention
The present invention relates generally to a power supply system designed to control AC power supply units disposed in cabinets, and more particularly to an improved structure of a power supply system capable of controlling the power supply to, for example, a building-block private branch exchange (PBX) system in a simple switching operation of an AC power supply unit installed in a main cabinet.
2. Background of Related Art
Usually, turning on and off power sources of key telephone units in the building-block PBX system requires controlling AC power supply units together which are disposed within a plurality of cabinets. In a conventional power supply system for the key telephone units, turning on and off the power sources of the key telephone units is achieved by manually operating a circuit breaker installed in a main cabinet.
Each of the cabinets is commonly designed to activate a backup battery when the AC power output is interrupted by the circuit breaker in the main cabinet. Thus, when the power output from the AC power supply unit in each of the cabinets is stopped completely, communication between the backup battery and the AC power supply unit is blocked using a battery shut-off switch.
The above conventional power supply system, however, has the following drawback.
The circuit breaker and the battery shut-off switches are usually turned on and off in a manual operation while front panels of the cabinets are opened. Energized circuit components are, thus, exposed to the outside undesirably, which does not meet safety standards.